The present invention relates to textile engineering, and more particularly it relates to drawing mechanisms of textile machines, and the invention can be utilized most effectively in ringless spinning frames.
Drawing mechanisms incorporated in spinning, draw, etc. frames comprise a rotatable feed couple and a rotatable delivery couple between which the fibrous feed material is drawn and thinned, this feed material being sliver, roving, etc. The ratio of the speeds of the feed and delivery couples defines the draft of the fibrous material. The feed couple includes a feed cylinder rotatable by a drive motor, an endless bottom belt running about this feed cylinder and being rotatable thereby, and a known per se guide engaged by this belt.
Furthermore, the feed couple includes an elastic pressure roller about which runs the top belt rotatable by the friction engagement with the bottom belt. The top belt also runs about a movable guide of the belts (cf. the FR Pat. No. 2,094,211 and the FRG Pat. No. 1,189,897). The fibrous material is made to pass between the bottom and top belts.
The delivery couple includes a delivery cylinder driven from an independent drive motor and an elastic pressure roller maintained in friction engagement with the delivery cylinder.
As a rule, in spinning frames the feed cylinders are integral structures extending the entire length of the frame, while the pressure rollers with the movable guides are mounted in pairs, one pair for one working station. The maintenance of a machine of this type is impeded; thus, to replace worn bottom belts, it is necessary to dismantle the entire feed cylinder line. Besides, the replacement of worn top belts serving one working station results in idling of the adjacent working station paired with the first-mentioned one with respect of the top belts. This makes for the simplicity of high-efficiency equipment.
There are known drawing mechanisms (cf. the U.S. Pat. No. 3,359,713, Cl. 57-36, dated 1966) comprising a housing and a feed couple defined by two endless belts, and a delivery couple, mounted in a cantilever fashion per each working station. One of the endless belts, namely, the bottom one, is mounted on its own feed cylinder and drives for rotation the other belt, the top one, mounted on the pressure roller of this couple. The delivery couple has its own driving cylinder and its own pressure roller. The feed couple further includes a stationary bottom belt guide and a movable top belt guide about which the respective belts are adapted to run in engagement therewith. Mounted at the inlet of the feed couple is a compacting device adapted to precompact the fibrous feed material. The feed and delivery couples are rigidly fixed in the housing, the spacing of their centers being short of the sum of their radii. This provides the loading of the feed and delivery cylinders, owing to the effort of the deformation of the resilient coatings of the pressure rollers.
This structure of the drawing mechanism is not, however, free from serious disadvantages arising from the fact that should the fibrous material become wound about the pressure rollers, which situation might take place in drawing mechanisms on account of sticking of fibres or strands of fibres, caused by their being electrically charged, or greased, or polluted, this would lead to an emergency seriously affecting the drawing process and its stability and complicating the maintenance of the drawing mechanism.
This feature negatively affects the operation of the machine, as a whole, and brings down its output, by reducing its time utilization factor.